Dynamically balanced centrifugal fan

Abstract

A method for dynamically balancing a centrifugal blower fan wheel is disclosed. The method includes the steps of determining an amount and location of change in the fan inlet ring of the blower wheel which is required to balance the blower wheel. Once this determination is made, the radial thickness of the inlet ring is increased at a predetermined location to provide the proper amount of balance to the blower wheel. A mold is described for accomplishing this method.

What is claimed is: 
     
       1. A fan blower wheel, comprising: a central hub portion;   a plurality of fan blades disposed radially around the central hub portion; and   a generally circular fan inlet ring supporting said plurality of fan blades at an end opposite said central hub portion, said inlet rings including a generally uniform, Z-shaped cross-section around its circumference, said Z-shaped cross-section including a first generally vertical portion, a generally horizontal portion, and second generally vertical portion, and including an area of greater cross-section than said uniform cross-section, said area being disposed at a predetermined location in a plane of the inlet ring to provide balance to said blower wheel; wherein said area of greater cross-section and said uniform cross section are formed as one piece.   
     
     
       2. A fan blower wheel according to claim 1, wherein said area of greater cross-section is formed concurrently and integrally with said inlet ring. 
     
     
       3. A fan blower wheel according to claim 2, wherein said blower wheel is fabricated from a polymeric material by an injection molding process. 
     
     
       4. A fan blower wheel according to claim 1, wherein said inlet ring having a generally Z-shaped cross-section includes said first generally vertical portion extending axially along an outer diameter of said fan blades, said generally horizontal portion disposed over said plurality of fan blades, and said second generally vertical portion extending upward from said generally horizontal portion, said second vertical portion having a generally uniform cross-section around its circumference, said second vertical portion including an area of greater cross-section than said uniform cross-section, said area being disposed at a predetermined location to provide balance to said blower wheel in the plane of the inlet ring. 
     
     
       5. A fan blower wheel according to claim 4, wherein said second vertical portion is disposed radially inwardly from said first vertical portion, and said area of greater cross-section is disposed radially outwardly over said horizontal portion by a predetermined distance. 
     
     
       6. A fan blower wheel according to claim 5, wherein said area of greater cross-section of said second vertical member does not exceed an outer edge of said blower wheel.